Eocene Fossils: The Mines of Messel

In November 2015, it was my good fortune to tour a special exhibit of never-before-displayed fossils from the shelves of the Hessiches Landesmuseum Darmstadt. The fossils were shown in the Visitor’s Center at the Messel Fossil Pit.

Messel is, indeed, a mine and a tomb, but you won’t find the bridge of Khazad-dûm, a Balrog, or the tomb of Durin like in Tolkien’s Middle Earth Mine of Moria. The story of Messel is every bit as spectacular, though.

Messel Today

The Messel Pit Fossil Site near Darmstadt, Germany, was named a UNESCO World Heritage site in 1995. According to UNESCO, the site “is the richest site in the world for understanding the living environment of the Eocene, which occurred between 57 million and 36 million years ago.”

Messel is a Lagerstätte. With no direct English equivalent, “Lagerstätte” isa German word adopted into the vocabulary used in paleontology. “Lagerstätte” describes a sedimentary deposit with fossils demonstrating exceptionally good preservation—sometimes including fossilized soft tissues. Messel is especially helpful in providing information on the evolution of mammals. Completely fossilized mammals, including stomach contents, have been found in Messel.

Ukinrek Maars eruption April 6, 1977. Photograph courtesy of Russell. Alaska Department of Fish and Game

Explosive Beginnings

The Messel site was born in a series of volcanic explosions 47 million years ago. This wasn’t a volcano like the well-known Eyjafjallajökull of Iceland, Kilauea of Hawaii, or Mount St. Helens of Washington State. Those volcanos all have built up volcanic cones above ground in multiple eruptions. A maar volcano, such as the one that formed Messel, erupts underground.

The eruptions are triggered by a column of magma moving towards the surface and encountering groundwater. Water turning to steam under such conditions expands 1,000 times in volume. This sudden expansion produces a steam explosion so violent that it shatters the overlying rocks and ejects them along with steam, ash, and magma. Typically, the deposits travel straight up and fall back on or near the site, producing a ring of deposits around the site and exposing a funnel-shaped mouth. A maar erupts until the available magma is cooled off or the available groundwater is exhausted.

The most recent maars to form are the East and West Ukinrek Maars in the Seward Peninsula, Alaska. They were the result of 10 days of explosive activity in March and April 1977. As is typical of most maars, they have since filled in with groundwater, glacial melt, and rainfall.

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